At this time was begun the practice, which virtually amounted to exemption, of making special details from the army to perform certain kinds of skilled labor. The first details thus made were to manufacture shoes for the army.[179] The list of those who might claim exemption, in addition to those named in the act of April 21, 1862, was extended to include the following: state militia officers, state and Confederate clerks in the civil service, railway employees who were not common laborers, steamboat employees, one editor and the necessary printers for each newspaper, those morally opposed to war, provided they furnished a substitute or paid $500 into the treasury, physicians, professors, and teachers who had been engaged in the profession for two years or more, government artisans, mechanics, and other employees, contractors and their employees furnishing arms and supplies to the state or to the Confederacy, factory owners, shoemakers, tanners, blacksmiths, wagon makers, millers, and engineers. The artisans and manufacturers were granted exemption from military service provided the products of their labor were sold at not more than seventy-five per cent profit above the cost of production. On every plantation where there were twenty or more negroes one white man was entitled to exemption as overseer.[180] In the spring of 1863 mail contractors and drivers of post-coaches were exempted;[181] and it was ordered that those exempted under the so-called "twenty-negro" law should pay $500 into the Confederate treasury; also, that such state officials as were exempted by the governor might be also exempted by the Confederate authorities. The law permitting the hiring of substitutes by men liable to service was repealed on December 28, 1863, and a few days later even those who had furnished substitutes were made subject to military duty.[182]